John bae



J. RAE. Grinding Mill.

No. 233,278'. Patented Oct. 12,1880.

UNITED STATES PATENT OFFICE.

JOHN BAE, OF NEW YORK, N. Y.

GRINDING-MILL.

SPECIFICATION forming part of Letters Patent No. 233,278, dated October 12, 18.80.

Application led February 10, 1879.

To all whom it may concern Be it known that I, JOHN RAE, of New York city, in the State of New York, have invented certain new and useful Improvements relating to Grinding-Mills, of which the following is a specification.

I mount two circular plates or disks with grinding-surfaces on separate axes contiguous to each other, so that theback face of one and the front face of the other shall rub together. The axes are not parallel to each other, but are so skewed that the opposed surfaces at the lower portion thereof, or at a point a suitable distance from the top, shall be very close together, while the upper portion shall be at an appreciable distance apart. The disks are conical, or rather conoidal, with the conical faces slightly hollowed. Being revolved in different directions, with their upper parts turning toward each other, the motion of the opposed surfacesby which I mean those parts of one wheel which are overlapped by a portion of the other wheelis downward. By this form of the surfaces and the Obliquity of the axes I draw in the material freely, and as the surfaces gradually close together bring it between parts which move across each other, and properly grind it, and then promptly discharge it.

My improved :mill is capable of working material very rapidly and delivering it finely ground with little friction, and consequently little heating.

The parts which I have termed disks77 may be made of any reasonable thickness, and made of stone, or of metal to inclose and confine stone; but however made, and especially when, as in some of my experiments, made of metal alone, it will be obvious that the small amount of heat generated in the grinding will be rapidly dissipated by the great surface presented, and when the disk is metal the dissipation of heat is aided by its high conducting power. The disks each move independently and uncovered, with their faces exposed both to radiation and to the cooling iniiuence of the air, which is freely in contact therewith. From all these causes the mill grinds cooler than any other known to me.

The invention may be applied to grinding a great variety of material of various physical qualities. I esteem it most importantfor those materials which are injured by a rise of temperature.

The accompanying drawings form a part of this specification, and represent what I consider the best means of carrying out the invention.

Figure 1 is a plan View, showing the parts with the top casing removed. Fig. 2 is a vertical section. The remaining figures show details on a larger scale. Fig. 3 shows one of the shafts and the collars by which it is held against end motion. Fig. 4 is a section through a part of one of the disks. Fig. 5 is a section through the corresponding part of the opposite disk. Fig. 6 is a diagram, showing the relative positions of the grinding-disks when seen in side elevation. Fig. 7 is a diagram, showing the same in edge view, with the inclination exaggerated.

Similar letters of reference indicate like parts in all the figures.

A is the fixed fram work, and A a light casing, which, with theframe-work A, makes a tight box, which iucloses all the dust which might escape from the grinding.

A2 is a fixed funnel or hopper supported by braces A3 A3, and of a thin or wedge form at its lower end, adapted to guide the grain or other article to be ground into the narrow space presented between the two opposing surfaces of the wheels or disks which effect the grinding.

The disk B is mounted on a shaft, b, which is horizontal, and stands squarely with the frame. The disk C is mounted on a shaft, c, which is oblique in both directions-that is to say, it is inclined out of a horizontal, and itis also skewed or oblique when seen in plan.

The axes b o are at a distance apart only a little greater than the semidiameters of the corresponding disks B O.

The disks are presented with a portion of the face of each covered by or presented against 9 5 acorrespondingportion of the face of the other.

The grinding operation is all effected in the portion marked B O in the diagram, Fig. 6. 'Ihe surfaces are in contact, or nearly so, at the bottom, and are sufficiently wide apart at roo the top to receive the material which is to be ground.

The material, received through the hopper or otherwise into the wide-apart portion of this space B' C at the top, is drawn down, crushed, ground, and delivered below in a finely-disintegrated state with a rapidity dependent on the velocity with which the disks are rotated, but which, by the construction of the mill, is intended to be in all cases very great.

The shaft b is intended to be immovable endwise. It may be provided with a stout setscrew (not represented) pressing against each end in the manner shown at the pulley end of the shaft c.

The shaft chas a set-screw, D, tapped through a stout bracket, A", which forms a part ot' the fixed frame-work. The screw bears against the end of the shaft c. Its bearing end should be slightly spherical, and a jam-init (not represented) set tightly against the bracket A* may aid in holding the screw very solidly in any position in which it is adjusted. This prevents the disk O from moving too closely against the disk B when the mill runs empty. The other end of the shaft c is equipped with means which are not only adjustable, but also elastic. It allows the shaft c, with its disk O, to move in the direction to increase the distance from B.

G is a. plate, which bears against the end of the shaft c, and is formed with a hole near each end, receiving a bolt, H. Each bolt H presses, either directly or through a suitable Washer, against a thick spring, I, which, in turn, bears against the plate G.

In adjusting the mill for use the bolts H are set up so as to press the springs I with considerable force against the plate G, and consequently to press the latter against the end of the shaft c. It being understood that the bearings of the shaft c are not collared, but are cylindrical, the yielding when any too hard substance or too great quantity of material is received from the hopper between the grinding surfaces will be readily understood.

I can drive both shafts b c by an indepeiident belt from a counter-shaft, (not sliown,) or I can drive both by a single belt running properly in contact with the driviiig-pulley on each shaft.

J is a tightening-pulley, which may be set up and down within considerable limits, and serves, when the parts are thus driven, not only to maintain the belt at the proper tightness, but, by causing the belt to hug around a greater portion of the periphery of the pulley on B, promotes the conveyance of a proper quantity of power to that shaft. Ordinarily the shafts b c will be geared together, in addition to a proper arrangement of the belts t0 drive them.

I think the surfaces of the disks which are presented toward each other tend to become slightly hollow by use. That is to say, the disks are thicker in the middle than at the periphery, and the surfaces, instead of being true cones, are conoids, the line from the center to the periphery beingr slightly curved inward. I make them so in the rst instance. In Figs. 4 and 5 the faces are intended to be thus slightly liollowed.

Modifications may be made. The hopper may be dispensed with and the material supplied by other means. Agitators, force-feeders, or other devices may be employed for supplyiii g the material to be ground.

The faces of the disks may be formed with burr-stone or other ordinary or suitable refractory material, secured in any reliable way in or upon the wheels, which I have termed disks The ground material may be conducted away continuously through a spout or other ordinary or suitable means. I have shown simply a box, K, to form a receiver for the ground matter. Air may be introduced through the centers of the shafts or otherwise, to promote ventilation and coolness.

Obviously the bearings may be widened and protected, by stufIng-boxes, leather, or other means, against the entrance of grit in grinding earthy matter.

Instead of mounting the skewed shafts c skewed in both directions, they may both lie in the same horizontal plane, in which case the disks would approach nearest to each other at the middle of the opposed or overlapped portions instead of at the bottom, or they may lie so that they appear parallel in plan view, the Obliquity being all in the inclination from the horizontal, or only seen in the end view. I have experimented successfully with the shafts mounted in this latter position. I propose to employ adjustable boxes with set-screws to vary the Obliquity.

The tendency of my mill is to wear the surfaces with a very close approach to uniformity. The center of each stone or wheel within the line of rubbing should be sunk outof' contact.

I claim as my invention- The grindiugmill described, having the disks B G, with slightly hollow coiioidal faces, and arranged as described, iii combination with the hopper A2, adjusting means D G H, and yielding springs I, as herein specified.

In testimony whereof VI have hereunto set my hand this 6th day of February, 1879, in the presence of two subscribing witnesses.

Witnesses: JOHN RAE.

E. B. BoL'roN, CHARLES C. STETSON.

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